1. Field of the Invention
The invention relates in general to a display panel and a mother substrate thereof, and more particularly to a display panel which has buffering metal layer and is capable of being cutting by laser and a mother substrate thereof.
2. Description of the Related Art
Diamond knife, water cutter knife and laser cutting are often used in glass cutting technology. During laser cutting, the heat generated by a laser source breaks glass molecular bond first and then the broken molecules are cooled down by a cooling device next. Then, the glass is divided due to thermal expansion and contraction.
Referring to both FIG. 1A and FIG. 1B. FIG. 1A illustratively shows a LCD mother substrate cut by a conventional laser cutting technology. FIG. 1B illustrates an enlarged portion of the top and the bottom mother substrates and the sealant of FIG. 1A, and the portion close to a predetermined laser cutting line. The LCD mother substrate 10 typically comprises a first mother substrate 11, a second mother substrate 13 assembled with the first mother substrate 11 by a sealant 16, and a liquid crystal layer (including numerous LC molecules) disposed therebetween. The first mother substrate 11 and the second mother substrate 13, for example, are respectively a mother substrate having a color filter layer and a mother substrate having many transistors. Many LCD panels 15 can be formed by laser cutting the first mother substrate 11 and the second mother substrate 13. Each display panel 15 has a display area 51 and an IC bonding area 53, wherein the sealant 16 is disposed around the display area 51. As indicated in FIG. 1A, the laser light C cuts the first mother substrate 11 along the predetermined laser cutting line 19 of the first mother substrate 11.
Referring to FIG. 1B, a metal black matrix or a resin black matrix 17 is normally disposed between the first mother substrate 11 and the sealant 16. In addition to the resin black matrix 17, the organic material layers disposed under the first mother substrate 11 (i.e. comprising the color filter layer) could further include an overcoat 18. During laser cutting, the laser beam 30 is normally deformed into a long ellipse whose width D30 ranges between about 1˜1.4 mm. Also, the distance between the black matrix 17 and the predetermined laser cutting line 19, and the distance D16 (illustrated in FIG. 1A) between the edge of the sealant 16 and the predetermined laser cutting line 19 generally range between about 0.3˜0.5 mm. As the distance may further be reduced to 0.2 mm in some special designs, the width D30 of the laser beam 30 is obviously larger than the distance. As laser cutting is a heat treatment process, the materials underneath the glass such as the sealant 16 and the organic material layer(s) will be affected by the heat generated during laser cutting on the first mother substrate 11 or the second mother substrate 13 made from glass. For example, the organic material layer(s) such as the resin black matrix 17 and the overcoat 18 of the first mother substrate 11 of FIG. 1B which can only resist about 200° C. will be affected. Furthermore, along with the advance in the industry, the distance D16 between the sealant 16 and the edge of and the predetermined laser cutting line 19 becomes shorter and shorter, the first mother substrate 11 and the second mother substrate 13 also become thinner and thinner. When laser cutting is performed on a thin glass mother substrate, the heat radiated downwards will severely affect the sealant 16, the resin black matrix 17 and the overcoat 18 (the organic material) which are positioned close to the cutting line. The sealant 16 and the organic material may be melted, cracked or peeled off, hence the LCD panel 15 is damaged and the yield of production is deteriorated.
Thus, how to avoid the heat of the laser beam damaging the sealant 16 or the organic materials of the mother substrate close to the laser cutting lines has become an imminent issue to be resolved.